The present invention relates generally to pointing devices for use in connection with computers and other electronic instruments and devices. More specifically, the present invention relates to a pointing device used to move a pointer or cursor on a display of a computer or similar electrical or electronic device or instrument.
Many operations relating to the use of modern computers, and in particular personal computers, require that a pointer or cursor be placed in a particular location on a display screen. In addition, many computer-operated and video games are operated based on positioning the cursor or pointing device in a particular location.
In some applications, the position of the cursor may be governed by a touch pad, which is a small touch-sensitive pad embedded in the casing of the device or instrument. Pressure applied to different portions of the pad controls the movement of the cursor on the screen.
In other applications, a joystick is used to control the movement of the cursor. On some laptop computers, this joystick may be a very small device positioned between several of the keys on the keyboard. The computer user manipulates such a small joystick by the end of the user's finger. On many computer games, and in other applications, the joystick may be somewhat larger, and be manipulated by the user grasping the entire joystick with the user's hand. Other applications may use joysticks of different sizes to manipulate a position indicator on the screen. The present invention will be described in connection with its application to joysticks.
The position of the joystick, and its movement relative to its central "rest" or "neutral" position, should be identified so that such position information can be transferred to place the cursor at the appropriate spot on the computer screen or display. A variety of devices have been designed for detecting the position of a joystick. One particular mechanism for a pointing device is described in U.S. Pat. No. 5,640,178 to Endo et al. This reference describes a joystick mounted on a resilient substrate. Strain gauges are formed on one surface of the substrate. A voltage is applied across a pair of the strain gauges in a particular direction, and the voltage at a half bridge output terminal between the strain gauges is measured. From this voltage, the amount of strain on each of the strain gauges of the pair may be determined. From that information, position information can be interpreted. However, this measurement technique requires that the strain gauges of the pair be exactly matched, with exactly equivalent properties. In one embodiment, the strain gauges are formed in a particular configuration so they can be laser trimmed to ensure that the strain gauges have identical properties.